The present invention relates to the art of fluxes for arc welding and more particularly to a granular flux suitable for submerged arc electric welding of the type including agglomerated or fused particles containing fluxing ingredients with or without normal alloying constituents. The invention is particularly applicable for use with agglomerated fluxes used in submerged arc electric welding and it will be described with particular reference thereto; however, the invention has broader applications and may be used with fused particles of fluxing constituents, with or without alloying and other materials contained therein. This invention may also be used to advantage when applied to the fill components of cored electrodes or to the coating components of SMAW manual electrodes. It may be applied directly to the jacket and/or into the seam of cored electrodes or to the core wire of SMAW manual electrodes. The invention is further particularly applicable to the welding of high strength low alloy steels such as HY-80, HY-100 and even HY-130 and it will be described with particular reference to fluxes of the type used in welding such high strength, low alloy steels although the invention is not limited to any particular type of flux. However, the invention relates to reduction of diffusible hydrogen to levels approaching less than 5.0 ml/100 grams of deposited weld metal (hereafter "ml/100 g") and preferably less than 3.0 ml/100 g. Metals with yield strengths greater than 102,000 psi minimum yield strength must have, by specifications, less than 3.0 ml/100 g and preferably less than 2.0 ml/100 g. Such reduced level of diffusible hydrogen is a primary factor when welding high strength low alloy steels having a yield strength in excess of 80,000 lbs/in.sup.2.
High strength, low alloy steels are noted for their toughness, particularly at low temperatures and have been used extensively in the fabrication of cryogenic vessels and large transportation equipment, especially railroad cars, surface ships and submarines. These vessels have plates of high strength, low alloy steels welded together to form fabricated structures. It is axiomatic that such welds must have low diffusible hydrogen to prevent hydrogen induced cracking. The present invention relates to an improvement in the normal agglomerated or fused flux used for submerged arc welding of mild steel and high strength, low alloy steels. The invention is applicable to any submerged arc welding process where reduction of said diffusible hydrogen is desired, such as welding of mild steels, especially thick plates of mild steel as done in support structures for offshore drilling platforms.
When using submerged arc welding for high strength steel, high deposition rates and high quality welding have involved the use of specific fluxes which tend to create a low level of diffusible hydrogen as measured by the standard American Welding Society hydrogen analysis test identified as AWS A4.3(1986). In the past, these fluxes have normally resulted in a diffusible hydrogen level in the weld bead of between 5.0 and 10.0 ml/100 g diffusible hydrogen. Fluxes have been formulated which attempt to decrease this diffusible hydrogen value to less than 5.0 ml/100 g; however, such fluxes in submerged arc welding have resulted in diffusible hydrogen of over 3.0 ml/100 g. This level of diffusible hydrogen may be acceptable at 80,000 psi yield strength when used with proper procedure control; however, specifications are now in place which demand substantially lower diffusible hydrogen to prevent the hydrogen induced cracking of the weld or heat affected zone (HAZ). In addition, in the higher strength steels, fabricators are demanding less than 2.0 ml/100 g of diffusible hydrogen in the resulting weld bead. These levels have been extremely difficult, if not impossible, to obtain in submerged arc welding in view of the ambient conditions under which such welding takes place and the effect of the moisture content in the air surrounding the welding operation. Consequently, there is a demand for a submerged arc welding flux which will reduce the diffusible hydrogen in the resulting weld bead to below 3.0 ml/100 g and preferably below 2.0 ml/100 g, especially when welding higher strength metal such as HY-100 and HY-130. Fluxes heretofore have not been able to accomplish this objective economically and repeatedly in various welding environments experienced when using submerged arc welding techniques.